Oxide materials like blast furnace slag, steelmaking slag, iron ore, etc. are typically prepared for analysis using a procedure involving fusion in low melting point flux. In the case of analysis by x-ray fluorescence, the melt can be poured into a casting dish and the resulting bead needs no further preparation. In the case of solution methods of analysis, such as AAS (atomic absorption spectrometry), DCP (direct current plasma optical emission spectrometry), and ICP (inductively coupled plasma optical emission spectrometry), the melt may be slowly poured into a beaker of dilute aqueous acid and dissolution will be very rapid.
The substitution of automatic devices for manual methods of manipulating the melt's container during fusion is desirable for many objectives, including lower direct labour cost, longer life of the melt container or containers, shorter preparation time per sample, multiple samples prepared in time parallel fashion, uniform quality of performance, improved accuracy and repeatability.
There has been some evolutionary development of automatic fusion devices, but these prior art techniques suffer from one or more of the following disadvantages:
(1) high initial cost
(2) high operating cost
(3) short mean time before failure
(4) long mean time to repair
(5) inadequate accuracy and repeatability
(6) inadequate confidence that a useful sample will result each time a sample is prepared (due to cracking of the bead, sticking of the bead, the bead being too thin on one edge or too thick on the other edge, or the bead not completely filling the bottom of the casting dish).
One related prior patent is Canadian Pat. No. 1,011,556, issued June 7, 1977 to Fernand Claisse and entitled "Fusion And Casting Machine". The machine disclosed in this prior patent requires frequent adjustment to provide good quality beads. It is fairly complex with many moving parts, and therefore tends to fail too frequently in our experience. The time taken to make repairs is often excessive.
Another patent related to this subject matter is U.S. Pat. No. 4,138,209, issued Feb. 6, 1979, to Warner Bahr, and entitled "Apparatus For Automatically Melting And Casting Fusible Material". In this patent, the mechanism does not provide a motion which would ensure that the particles on the sidewalls of the crucible are "washed" into the melt. If there are undissolved particles on the sidewalls, and some of these particles are washed into the casting dish along with the melt, then one of two unsatisfactory conditions will arise:
(1) the bead will crack because of the discontinuity of the undissolved particle, or if it does dissolve,
(2) the bead will not crack, but there will be a locally high concentration of certain elements in the bead.